The Celtic cross is a form of Christian cross featuring a nimbus or ring that emerged in Ireland, France and Great Britain in the Early Middle Ages. A type of ringed cross, it became widespread through its use in the stone high crosses erected across the islands, especially in regions evangelized by Irish missionaries, from the ninth through the 12th centuries.

A high cross or standing cross is a free-standing Christian cross made of stone and often richly decorated. There was a unique Early Medieval tradition in Ireland and Britain of raising large sculpted stone crosses, usually outdoors. These probably developed from earlier traditions using wood, perhaps with metalwork attachments, and earlier pagan Celtic memorial stones; the Pictish stones of Scotland may also have influenced the form. The earliest surviving examples seem to come from the territory of the Anglo-Saxon kingdom of Northumbria, which had been converted to Christianity by Irish missionaries; it remains unclear whether the form first developed in Ireland or Britain.